Clathrate of Azithromycin Hydrate With 1,2-Propyleneglycol, Method For The Manufacture Thereof, And Pharmaceutical Composition containing same

ABSTRACT

The present invention relates to a clathrate of azithromycin hydrate with 1,2-propyleneglycol of formula (I), a method for the manufacture thereof, and a pharmaceutical composition containing same. The inventive compound is much less hygroscopic than azithromycin hydrate or crystals known in the art, therefore, it can be useful for the preparation of a medicine for treating various microbial infections.  
                 
wherein m ranges from 1 to 2 and n, from 0.30 to 0.45.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1: a powder X-ray diffraction spectrum of the compound of thepresent invention;

FIG. 2: a powder X-ray diffraction spectrum of azithromycin monohydrate;

FIG. 3: a powder X-ray diffraction spectrum of azithromycin dihydrate;

FIG. 4: a differential scanning calorimetric scan of the compound of thepresent invention;

FIG. 5: a differential scanning calorimetric scan of azithromycinmonohydrate;

FIG. 6: a differential scanning calorimetric scan of azithromycindihydrate;

FIG. 7: comparative hygroscopic properties of the compound of thepresent invention, azithromycin anhydride, monohydrate, and dihydrate.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to a novel clathrate of azithromycin hydrate with1,2-propyleneglycol, a method for its manufacture, and a pharmaceuticalcomposition containing the clathrate.

Azithromycin, 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A(N-methyl-11-aza-10-deoxo-10-dehydroerythromycin A: IUPAC) of formula(II) disclosed in U.S. Pat. Nos. 4,517,358 and 4,474,768, is anazalide-type semi-synthetic macrolide antibiotic, useful for treatingbronchial infection, sexual contact infection and dermatologicalinfection (see Kirste and Sides; Antimicrob. Agents Chemother., 33, 1419(1989)).

Azithromycin is known to exist in three forms, the anhydride,monohydrate and dihydrate forms. These forms have been identified bypowder X-ray diffraction and differential scanning calorimetric studies,and have different water stabilities.

As disclosed in U.S. Pat. No. 4,517,359, azithromycin anhydride (m.p.113-115° C.) can be obtained by evaporating solvent (e.g., chloroform)in the course of preparing azithromycin. However, since azithromycinanhydride is non-crystalline product, its highly hygroscopic property isnot suitable for pharmaceutical formulation.

Further, azithromycin monohydrate (m.p. 136° C.), as described in U.S.Pat. No. 4,474,768 and WO Publication No. 89/00576, is crystalline butit has also hygroscopic property, making it difficult to maintain itswater content at a constant level.

WO Publication No. 89/00576 discloses a process for preparingazithromycin dihydrate (m.p. 126° C.) from azithromycin monohydrate byrecrystallizing from a mixture of tetrahydrofuran, water and a C₅˜C₇aliphatic hydrocarbon.

Although the dihydrate is less hydroscopic than the monohydrate, thewater content thereof must be carefully maintained during a vacuumdrying (controlled to be a water content of 4.6%±0.2, and a volatilecomponent content of less than 0.25%) step at a relatively lowtemperature. Such a water content controlling procedure is, however, notsufficient for removing the toxic aliphatic hydrocarbon solvent such asn-hexane (classified as second grade by ICH (International Conference onHarmonization of Technical Requirements for Registration ofPharmaceuticals for Human Use)) rigorously used in the recrystallizationprocedure. On the other hand, vacuum drying in higher temperature mayresult in formation of azithromycin dihydrate having undesirable watercontent. Further, the preparation of the dihydrate requires a highproduction cost.

Accordingly, many attempts have been made to develop a novel crystal orsolvate form of azithromycin. For example, EP Publication No. 0,984,020discloses a clathrate of azithromycin monohydrate with isopropanol offormula (III).

WO Publication No. 00/32203 discloses an ethanol solvate of azithromycinhydrate of formula (IV).

wherein, x is a molar equivalent of water such that the water contentcan range from 2.0 to 4.0%, and y a molar equivalent of ethanol suchthat the ethanol content can range from 1.5 to 3.0%.

Further, WO Publication No. 99/58541 discloses a solvate of azithromycinwith a non-halogenated solvent, European Patent No, 0,941,999 A and U.S.Pat. No. 5,869,629 discloses a method for preparing azithromycindihydrate from azithromycin monohydrate using acetone and water.However, there has existed a need to develop an improved crystal form ofazithromycin crystal suitable for pharmaceutical applications.

The present inventors have endeavored to develop a novel clathrate ofazithromycin having good water-stability, and found that a clathrate ofazithromycin hydrate with 1,2-propyleneglycol obtained by dissolvingazithromycin in acetone containing 1,2-propyleneglycol and thenrecrystallizing with water can be prepared at a high yield and be usefulfor the preparation of a medicine for treating various microbialinfections

It is, therefore, an object of the present invention to provide a novelclathrate form of azithromycin, a method for the manufacture thereof,and a pharmaceutical composition comprising same.

In accordance with the present invention, there is provided a novelclathrate of azithromycin hydrate with 1,2-propyleneglycol of formula(I):

wherein m ranges from 1 to 2 and n, from 0.30 to 0.45.

The present invention further provides a process for preparing theclathrate of formula (I), comprising the steps of: (1) dissolvingazithromycin in acetone then adding 1,2-propyleneglycol and waterthereto to obtain a crystalline product; and (2) filtering the crystalsformed, washing the crystals with water and drying at 40 to 45° C. for12 to 24 hours.

The present invention also provides a pharmaceutical composition fortreating microbial infection, comprising the clathrate of formula (I)and a pharmaceutically acceptable carrier or delivery system.

The compound of formula (I) may be prepared by dissolving azithromycinin a suitable amount of acetone, preferably 2 to 10 ml of acetone per gof azithromycin, adding 1,2-propyleneglycol thereto in an amount of 0.25to 2.5 ml based on 1 ml of acetone while maintaining at a temperatureranging from room temperature (R.T.) to the boiling point of acetone,adding water in an amount of 1 to 3 ml per ml of acetone, stirring themixture for 30 minutes to 4 hours at a temperature ranging from 0° C. toroom temperature, filtering precipitated crystals, washing the crystalswith water and drying for 12 to 24 hours at a temperature ranging from40° C. to 45° C.

The 1,2-propyleneglycol moiety of the inventive clathrate is essentiallynon-toxic (LD₅₀: 25 ml/kg, at oral administration in rat), and it canexist in the form of a racemate, an S-isomer, or an R-isomer.

The azithromycin being used in the preparation of the inventiveclathrate may be anhydride, monohydrate, dihydrate, isopropanolclathrate, or ethanol solvate of azithromycin known in the art or amixture thereof, and it can be prepared by any of the methods disclosedin U.S. Pat. Nos. 4,517,359 and 4,474,768 and Korean Patent ApplicationNo. 2001-14659.

The novel clathrate compound of the present invention meltsapproximately at 130° C., shows in a DSC scan an endothermic peak at150.8° C. and heat capacity of 104.42 J/g, as shown in FIG. 4. Thesethermal properties are completely different from those of themonohydrate form (endothermic peak 145.44° C.; heat capacity: 137.37J/g) or the dihydrate form (endothermic peak 142.72° C.; heat capacity:160.15 J/g), prepared by a known method (WO89/00576 and U.S. Pat. No.5,869,629).

The crystal structure of the clathrate compound of the present inventiondiffers from those of the monohydrate and dihydrate form, as the powderX-ray diffraction patterns shown in FIG. 1, FIG. 2 and FIG. 3,respectively.

The water content of the inventive clathrate determined by aKarl-Fischer water analyzer ranges from 2.3 to 4.4%, preferably, from3.0 to 4.0%, more preferably, from 3.1 to 3.7%, while its1,2-propyleneglycol content determined with a gas chromatography or¹H-NMR spectroscopy ranges from 2.83 to 4.27%, preferably, from 3.0 to3.6%.

The inventive clathrate of formula (I) preferably has an m value of1.5±0.2 and an n value of 0.35±0.2. However, these m and n values arenot intended to limit the scope of the present invention.

The clathrate compound of the present invention is much less hygroscopicthan azithromycin anhydride or azithromycin monohydrate, and its watercontent remains more or less constant when stored under a humidcondition, unlike azithromycin dihydrate.

The clathrate compound of present invention can be used in formulatingvarious pharmaceutical compositions for treating various microbialinfection. Such a composition contains the inventive clathrate togetherwith pharmaceutically acceptable excipients and carriers, which may beadministrated orally, injectably, rectally, transdermally, bucally ornasally. Suitable forms for oral administration include tablets,compressed or coated pills, dragees, sachets of powder forreconstitution, hard or soft gelatin capsules, syrups and emulsions etal. Suitable forms for parenteral administration include aqueous ornon-aqueous solution, emulsion, while for rectal administration suitableforms include suppositories with hydrophilic or hydrophobic vehicles.For topical application the invention provides ointments or aerosolformulations known in the art; for transdermal delivery, there areprovided suitable delivery systems as known in the art. For nasaldelivery there are provided suitable aerosol delivery systems known inthe art.

This invention will be better understood from the Examples that follow.However, the examples illustrate, but do not limit, the invention. Thoseskilled in the art will readily appreciate that the specific methods andresults discussed are merely illustrative of the invention as describedmore fully in the claims that follow thereafter.

EXAMPLE 1

100 g of azithromycin anhydride was dissolved in 300 ml of acetone and100 ml of 1,2-propylene glycol was added thereto. The solution wasstirred for 10 minutes at R.T. and 500 ml of water was added dropwisethereto to induce the precipitation of azithromycin crystals. Thesolution was stirred for 2 hours at R.T. and the precipitate wasfiltered, washed rigorously with water, and then dried at 40° C. for 20hours to give 96 g of a clathrate of azithromycin hydrate with1,2-propyleneglycol.

m.p: 129 to 131° C.,

The water content determined by a Karl Fischer water analyzer: 3.5 wt %,

The 1,2-propyleneglycol content determined with a gas chromatography:3.3 wt %.

EXAMPLE 2

20 g of azithromycin monohydrate was dissolved in 100 ml of acetone and15 ml of 1,2-propylene glycol was added thereto. The solution wasstirred for 10 minutes at R.T. and 200 ml of water was added dropwisethereto to induce the precipitation of azithromycin crystals. Thesolution was stirred for 2 hours at 0 to 5° C. and the precipitate wasfiltered, washed rigorously with water, and then dried at 40° C. for 20hours to give 18.2 g of a clathrate of azithromycin hydrate with1,2-propyleneglycol.

m. p: 130 to 132° C.,

The water content: 3.4 wt %,

The amount of 1,2-propyleneglycol: 3.2 wt %.

EXAMPLE 3

20 g of azithromycin monohydrate was dissolved in 120 ml of acetone and15 ml of 1,2-propylene glycol was added thereto. The solution wasstirred for 10 minutes at R.T and 180 ml of water was added dropwisethereto to induce the precipitation of azithromycin crystals. Thesolution was stirred for 3 hours at 0 to 5° C. and the precipitate wasfiltered, washed rigorously with water, and then dried at 40° C. for 20hours to give 17.6 g of a clathrate of azithromycin hydrate with1,2-propyleneglycol.

m.p: 130 to 132° C.,

The water content: 3.4 wt %,

The 1,2-propyleneglycol content: 3.5 wt %.

TEST EXAMPLE

The compound obtained in Example 1, azithromycin monohydrate anddihydrate obtained by the methods in accordance with U.S. Pat. No.5,869,629 were subjected to differential scanning calorimetricmeasurements (heat speed 10° C./minutes.). The inventive compound ofExample 1 showed an endothermic peak at 150.8° C. and heat capacity of104.42 J/g, as shown in FIG. 4. The azithromycin monohydrate, on theother hand, showed an endothermic peak at 145.44° C. and heat capacityof 137.37 J/g (FIG. 5), while azithromycin dihydrate, an endothermicpeak at 142.72° C. and heat capacity of 160.15 J/g (FIG. 6).

Further, the X-ray diffraction spectra of above three compounds areillustrated in FIG. 1, FIG. 2 and FIG. 3, respectively. The X-rayresults summarized in Table 1 show that the compound of presentinvention has a crystal structure which is completely different fromthose of the known compounds. TABLE 1 2 theta(°2 θ) d-value(A) I/Io(≧2)6.200 14.2437 3 7.300 12.0996 5 7.820 11.2962 32 8.220 10.7474 2 9.7409.0733 100 10.220 8.6482 2 11.140 7.9360 29 11.900 7.4308 7 12.2207.2369 6 12.500 7.0754 22 13.880 6.3749 12 14.640 6.0456 16 15.2205.8165 12 15.400 5.7490 12 15.700 5.6398 6 15.940 5.5554 6 16.620 5.32966 16.960 5.2235 10 17.220 5.1452 9 17.460 5.0750 11 18.060 4.9078 218.300 4.8439 3 18.500 4.7920 5 19.040 4.6573 12 19.660 4.5118 9 19.9804.4403 12 20.400 4.3498 10 20.860 4.2549 8 21.740 4.0846 4 22.320 3.97983 22.640 3.9242 5 23.220 3.8275 2 23.540 3.7762 3 23.960 3.7109 3 24.5203.6274 4 24.720 3.5985 3 25.260 3.5228 2 25.500 3.4902 3 26.200 3.3985 428.440 3.1357 2 31.080 2.8751 2 33.600 2.6650 2Radiation: Cu K-α1Divergence slit: 1°Scattering slit: 1°Receiving slit: 0.15 mmOperation: 40 kV/126 mAScan Mode: continuousScan speed: 5°/minScan step: 0.02°

Also, the hygroscopic properties of each of the compound obtained inExample 1 (1), azithromycin dihydrate (2), monohydrate (3), andanhydride (4) were determined by exposing each sample to a relativehumidity of each 25%, 50%, 75% or 100% for 7 days and measuring thewater content thereof by the Karl Fischer method. The result is shown inTable 2 and FIG. 7. TABLE 2 (1) (2) (3) (4) Onset 3.50 4.58(4.1)2.30(3.2) 0.22 Relative humidity 100% 4.06 6.11(5.2) 6.29(7.2) 7.00Relative humidity 75% 3.55 5.10(4.6) 5.41(6.6) 4.33 Relative humidity50% 3.50 4.25(4.6) 5.13(5.6) 2.85 Relative humidity 25% (33%) 3.014.20(2.5) 3.35(2.3) 1.11 Calculated water content (%) 3.38¹⁾ 4.60 2.350.00 Found-Calculated (Difference, %) −0.37˜+0.68 −0.4˜+1.51 +1˜+3.94+1.11˜+7.00 (−2.1˜+0.6) (−0.05˜+4.84) Range of Difference (%) 1.051.91(2.7) 3.94(4.9) 7.00Note:¹⁾Calculated based on m = 1.5 and n = 0.30 in formula (I).²⁾The numbers in parenthesis are values obtained after 3 days at thecorresponding relative humidity.

Table 2 clearly shows that the novel clathrate compound of the presentinvention is much less hygroscopic than other compounds.

The Effect of the Invention

In accordance with the present invention, a clathrate of azithromycinhydrate with 1,2-propyleneglycol is prepared from known anhydride,monohydrate, dihydrate or other crystalline form of azithromycin. Theinventive compound is much less hygroscopic than azithromycin hydrate orcrystals known in the art, therefore, it can be useful for thepreparation of a medicine for treating various microbial infections.

1-7. (canceled)
 8. A non-aqueous pharmaceutical composition for treatingbacterial infection, comprising a clathrate compound of azithromycinhydrate with 1,2-propyleneglycol of formula (I) and a pharmaceuticallyacceptable carrier: